The present invention relates in general to sheet handling apparatus for reproduction apparatus for example, and more particularly to a receiver sheet supply and feed apparatus, including a vacuum corrugation belt feeder and a positive air pressure separator.
In typical reproduction apparatus such as copiers or printers, for example, information is reproduced on individual cut sheets of receiver material such as plain bond paper or transparencies. Such receiver sheets are stored in a stack and fed seriatim when copies are to be reproduced. The sheet feeder for the reproduction apparatus must be able to handle a wide range of sheet types and sizes reliably and without damage. Sheets must be fed individually; that is, without misfeeds or multi-feeds.
Reproduction apparatus sheet feeders are typically of two types, vacuum feeders or friction feeders. One type of vacuum feeder is shown in U.S. Pat. No. 4, 169,676, issued Oct. 2, 1979, in the name of Russel. This vacuum feeder, commonly referred to as an oscillating vacuum feeder, includes an oscillating tube through which vacuum is applied to tack a sheet to the surface of the tube (sheet acquisition) for withdrawal from the sheet supply stack. Nip rollers, in cooperative relation with bearings on the tube downstream of sheet acquisition zone in a sheet feeding direction, urge a separated sheet from the sheet supply stack along a feed path away from the supply stack. While such feeder is considered to be highly effective, it does have some limitations in feeding extremely light or heavyweight papers. It is also noisy due to both its mechanical oscillation requirements and its need to utilize a high flow/high pressure vacuum source.
Another type of vacuum feeder is shown in U.S. Pat. No. 4,635,921, issued Jan. 13, 1987, in the name of Thomas. This vacuum feeder, commonly referred to as a vacuum corrugation feeder, includes a vacuum plenum for acquiring a sheet from a supply stack. The top sheets in the stack are levitated by fluffer (positive air pressure) jets. Ported belts entrained about the plenum are driven to transport a sheet vacuum tacked to the belts from the supply stack. This type of feeder is highly efficient but is still subject to misfeeds/multi-feeds, and has certain limitations with regard to the range of types of sheet materials that can be reliably handled.
Yet another type of vacuum feeder is shown in U.S. Pat. No. 4,184,672, issued Jan. 22, 1980, in the names of Watkins et al, and U.S. Pat. No. 4,327,906, issued May 4, 1982 in the names of Frolich et al. This type of vacuum feeder, commonly referred to as a vacuum picker or sucker, includes a plurality of cup-like structures connected to a vacuum source and movable to selectively pick up a sheet from a supply stack for transport from the stack. Such feeder requires a complicated mechanical arrangement to accomplish its desired pick up and transport function.
One type of friction feeder is shown in U.S. Pat. No. 4,374,212, issued Feb. 5, 1983, in the names of Martellock et al, and U.S. Pat. No. 4,381,860, issued May 3, 1983, in the name of Silverberg. This type of friction feeder, commonly referred to as a scuff feeder, includes a member (respectively shown as a belt or paddle wheel, but may also comprise a roller) which relies on frictional engagement with a sheet for removal of the sheet from a supply stack. Scuff feeders are of the simplest construction and are the cheapest to manufacture. However, since sheet materials exhibit a wide variation in friction characteristics, scuff feeders are the least reliable of the discussed group of feeders.